Once a Guardian, always a Guardian.

Pitch curses Jack, sending him to a world where no one truly believes in magic. Shame the curse didn't count on Jimmy Kirk.

Centuries after the battle with Pitch; Destiny demands the Man In the Moon release one of his Guardians to help aid Earth by becoming fully human so they can leave it and enter space. MIM agrees, on the condition that if anything happens to during the human-lifetime where the guardian is required, he will be released from his amnesia and remember who he really is...it does.

Jack Frost likes spending time in San Francisco. He's been a Guardian for over 200 years. This is, however, the first time an adult - aka Jim Kirk - has ever noticed him. One-shot.